Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance at Dec. 31, 2012	$ 1	$ 426	$ 1,334,965	$ (77,348)	$ (2,228)	$ 1,255,816
Balance (in Shares) at Dec. 31, 2012	90,165	42,649,098
Net income				188,715		188,715
Other comprehensive income, net of tax					2,228	2,228
Stock issuances under employee plans, including income tax benefits		$ 9	13,527			13,536
Stock issuances under employee plans, including income tax benefits, shares (in Shares)		874,538
Issuance of common stock in connection with preferred stock conversion, net of issuance costs		$ 120	(470)			(350)
Issuance of common stock in connection with preferred stock conversion, net of issuance costs (in Shares)	(36,600)	12,000,000
Amortization of stock-based compensation			9,015			9,015
Balance at Dec. 31, 2013	$ 1	$ 555	1,357,037	111,367		1,468,960
Balance (in Shares) at Dec. 31, 2013	53,565	55,523,636
Net income				215,865		215,865	[1]
Stock issuances under employee plans, including income tax benefits		$ 5	20,170			20,175
Stock issuances under employee plans, including income tax benefits, shares (in Shares)		512,602
Repurchase and retirement of common stock, net of expenses		$ (10)	(36,771)			(36,781)
Repurchase and retirement of common stock, net of expenses, shares (in Shares)		(1,008,000)
Amortization of stock-based compensation			8,469			8,469
Balance at Dec. 31, 2014	$ 1	$ 550	1,348,905	327,232		1,676,688
Balance (in Shares) at Dec. 31, 2014	53,565	55,028,238
Net income				213,509		213,509	[1]
Other comprehensive income, net of tax					5	5
Stock issuances under employee plans, including income tax benefits		$ 13	10,237			10,250
Stock issuances under employee plans, including income tax benefits, shares (in Shares)		1,350,984
Common stock dividends ($0.04 per share)				(4,851)		(4,851)
Repurchase and retirement of common stock, net of expenses		$ (6)	(22,067)			(22,073)
Repurchase and retirement of common stock, net of expenses, shares (in Shares)		(645,338)
Stock issuance in connection with merger, net of preferred stock conversion	$ (1)	$ 656	1,971,629			1,972,284
Stock issuance in connection with merger, net of preferred stock conversion (in Shares)	(53,565)	65,552,269
Amortization of stock-based compensation			15,624			15,624
Balance at Dec. 31, 2015		$ 1,213	$ 3,324,328	$ 535,890	$ 5	$ 3,861,436
Balance (in Shares) at Dec. 31, 2015		121,286,153

[1] Per share amounts do not add across due to rounding differences in quarterly amounts and due to the impact of differences between the quarterly and annual weighted average share calculations.